<div id="media-description-dialog" title="<?php echo __('File description'); ?>">
  <textarea><?php echo $description; ?></textarea>
  <script type="text/javascript">
    $('#media-description-dialog').dialog(
    {
      width:'auto',
      height:'auto',
      resizable: false,
      buttons:
      {
        "<?php echo __('Save'); ?>": function()
        {          
          $( this ).dialog( "close" );
          mediaDescriptionSave($(this).children('textarea').val(), <?php echo $field['id']; ?>, <?php echo $fileId; ?>);
        }
      }
    });
  </script>
</div>